JPS58112475A - Starting system for ac/dc converter - Google Patents

Abstract

PURPOSE:To stabilize the starting operation by reducing the DC voltage of an AC/DC converter in response to the variation in the frequency when the frequency of a turbine generator decreases lower than the prescribed value at the starting time. CONSTITUTION:When steam is fed to a turbine generator which is operated at a rated frequency without load and the frequency of the generator decreases lower than the prescribed value, the frequency deviation from a frequency deviation detector inputted to a control circuit 51 becomes negative. Thus, the output signal of the control circuit 51 becomes negative, and its output signal is inputted to a limiter 52. The limiter 52 applies the negative output proportional to the magnitude of the output of the control circuit 51 to a constant voltage control circuit 9 togethe with a reference value Edp and detected value Ed. Accordingly, the input of the circuit 9 decreases, and the DC voltage of the AC/ DC converter of the controlled result accordingly decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for starting an AC/DC converter directly connected to a generator so as to stably start up the AC/DC converter.

TECHNICAL BACKGROUND OF THE INVENTION Conventionally, there are various methods for starting an AC/DC converter.
A method is adopted in which the conversion device is deblocked at the electrical angle 9()0 by setting the electrical angle (hereinafter referred to as α) near 0, and after deblocking, the transition is controlled so as to reach a predetermined α. This method has the advantage that systematic disturbances can be relatively suppressed.

FIG. 1 shows an outline of an AC/DC converter employing this type of system. In the figure, AC bus 1
, 1' are connected via time variable transformers 2, 2' to converters 3, 3' consisting of, for example, a large number of thyristors connected in series and parallel, and by controlling the firing phase of each thyristor, converts into direct current or direct current into alternating current. 4 and 4' are smoothing reactors, 5 is target flow @41 path, 6.6' is a potential transformer (PT), and 7.7' is a potential current transformer (C/T).
) is shown. The control device in such a main circuit configuration is
It consists of constant current control circuits (ACR) s, s', constant voltage control circuits (8) 9, 9', etc. The constant current control circuit and the constant voltage control circuit each have a reference value r, 1
．． , Edp and the detected value 1,1, ]iEd is converted into a control voltage EC, and this control voltage E0 is controlled 81]
The voltage is input to the voltage selection circuits 10 and 10'.

The control voltage selection circuits 10 and 10' automatically select the control system that advances the control angle most among various types of control, and the control voltage E selected here. is subjected to upper and lower limit limits by the control voltage limiter circuits 11, 11', and is input to the ignition phase control circuits 12, 12'.

The ignition phase control circuit 12, 12' has a control voltage E.

Determine the firing phase proportional to K and output a firing command to the Zyristor. In an AC/DC converter configured in this way, one side is generally operated as a forward converter under constant current control by switching the current margin (Δ■), as is well known.
The other is operated as an inverter under constant voltage control.

Now, FIG. 2 shows a load start-up pattern when the above-mentioned start-up method is adopted in equipment having such a configuration. In addition, in Fig. 2, the current setting value Id at startup
p was assumed to be 10% of the rated value. Naturally, the smaller the current setting value Idp, the more the converter output voltage r(t
Although the systematic disturbance associated with
p cannot be less than 10 inches. That is, if it is less than 10%, there is a risk that the current will be interrupted, and as a result, the Zyristor element may be destroyed. Therefore, in conventional equipment, the minimum current setting is 10%. Also, iB
I! In FIG. 2, the time until the transmitted power rises to the 10th stage, ie, T1, is 200 ms to 3 (about 10 ma).

Problems with the Background Art Now, in FIG. 1, consider the case where the AC bus 1 is directly connected to a generator via a step-up transformer or the like. For example, there is a case where nuclear power is transmitted to a consumption area via an AC/DC converter. The same applies not only to nuclear power but also to thermal power. In nuclear power generation, when the rated load is taken from a no-load state, it is done slowly over a long period of time, an example of which is shown in Figure 3. That is, at the beginning of startup, the generator output G1 is a few steps above the rated value, the time of TI is several tens of seconds, the time from TI to T2 is about 10 minutes, and the generator output G is changed from the generator output G to the generator output Gz.
The time to start up from T2 to T3 (usually several tenths of the rated value) is about one day, and the time to start up from the generator output G2 to the rated output, that is, the time from T4 to T5 is about one hour. In the case of thermal power, if not nuclear power,
In any case, the load is started up at a speed that is incomparable to the load start-up speed of the AC/DC converter. Therefore, since the above-mentioned conventional starting method cannot be adopted in an AC/DC converter directly connected to a generator, there is a strong demand for a new starting method.

Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a starting method for an AC/DC converter that can stably start up an AC/DC converter that is directly connected to a starter machine. It is about providing.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an AC/DC conversion device directly connected to a generator. The converter is characterized in that it operates by reducing the DC voltage of the converter.

Examples of the invention An embodiment of the present invention shown in the drawings will be described below.

FIG. 4 shows an example of the configuration of an AC/DC converter according to the present invention. In the figure, 51 is a control circuit which is a combination of proportional, integral, differential elements, etc. and has a control function F (s), which is connected to the AC bus 1 (
The input is the output signal from a frequency deviation detector (not shown) that detects the deviation Δf of the frequency of 1') from a predetermined value (usually 50 Hz or 60 Hz), and the output signal from the frequency deviation detector 1' is proportional to the frequency deviation Δf. Convert to signal and output. Also,
52 is a limiter 1.52 which inputs the output signal of this control m1 circuit 5. The output is applied to the constant voltage control circuit 9 (1 or 9') together with the reference value Ed and the detected value Ed.

Here, the limiter circuit 52 limits the positive output from the control circuit 516- and does not send out that output, and the negative output is suppressed to its magnitude as described above. It is provided as a correction signal for the reference value Edp, so that the reference value Edp is made smaller in appearance.

Incidentally, in the above, the output signal from the control circuit 51 is obtained so as to reduce the frequency deviation Δf as a result.

Furthermore, the output of the limiter circuit 52 is actually configured to be applied to each of the constant voltage control circuits 9 and 9' in FIG. . Instead, the output of the constant voltage control circuit may be given priority to the selected constant voltage control circuit 9 or 9'. In addition, here, one converter 3 is operated by constant current control as a forward converter,
Assuming that the other converter 3' is operated as an inverse converter under constant voltage control, a case will be described in which the output of the IJ miter circuit 52 is applied to the constant voltage control circuit 9'.

Next, the main startup method based on this configuration will be described.

When steam enters the turbine generator, which is currently operating under no load at the rated frequency, the turbine torque corresponding to the generator 11 force G1 increases, causing the frequency to rise. If the AC/DC converter is deblocked at this time, one DC power Pd will rapidly become the minimum vehicle power (for example, 10%). In addition, as explained in Figure 3, the rise of turbine torque is slower than the rise of DC power Pd, so the reduction in generator speed due to the electrical output of the contracted generator being larger than the input mechanical torque is and the frequency decreases.

As a result, the frequency of the turbine generator decreases below a predetermined value, so that the frequency deviation Δf from the frequency deviation detector input to the control circuit 51VC becomes negative. When this frequency deviation Δf becomes negative, the output signal of the control circuit 5 also becomes negative and is input to the limiter circuit 52. This results in
The limiter circuit 52 outputs a negative output proportional to the magnitude of the output of the control circuit 5, to a reference value Ed, and a detected value E.
It is applied together with d to the constant voltage control circuit 9'. In this case, since the output of the limiter circuit 52 is negative, the output acts to apparently reduce the reference value Edp, and a smaller deviation output than originally is given to the constant voltage control circuit 9'. It will be done. Therefore, the input to the constant voltage control circuit 9' decreases, and the DC voltage Ed, which is the result of the control, decreases. Also, the direct current I
Since d is controlled to be constant at, for example, 10%, the DC power Pd decreases as the DC voltage Ed decreases. and,
DC power Pd decreases and turbine generator torque G1
If it becomes smaller than , the frequency of the generator will increase.

FIG. 5 shows the output and frequency response when this startup method is applied. In the figure, the torque of the Po butter turbine generator, Pd is the DC power, and Δf is the frequency deviation. As can be seen from the figure, the DC power Pd tends to increase rapidly due to deblocking of the AC/DC converter, but Δf
decreases, so the control of the present invention described above causes the DC power Pd9- to decrease and the frequency deviation Δf to recover to zero.

In this way, in the AC/DC converter having the above configuration in which the turbine generator is directly connected, when the frequency of the turbine generator decreases below a predetermined value at the time of startup, the turbine generator frequency deviation Δf, that is, the frequency fluctuation The AC/DC converter is operated by reducing the DC voltage Ed of the AC/DC converter.

Therefore, the DC power Pd is made to match the turbine generator output, and the frequency is maintained at a predetermined value while being directly connected to the generator [
The starting operation of the AC/DC converter can be performed extremely stably.

It should be noted that the present invention is not limited to the above embodiments,
This can also be implemented as follows.

FIG. 6 shows a configuration of another embodiment according to the present invention, and the same parts as in FIG. 4 are denoted by the same reference numerals. The 61st part is the limit 5 in Figure 4. circuit 52
The signal obtained by adding the upper limit value UP to the output of the previous n1 control voltage limit 1. This signal is applied to the main control circuit @1 (or 11').
It is configured to set the upper limit value of the voltage limiter circuit 11 (or 11').

In such a configuration, as described above, when the DC power increases at startup and the frequency deviation Δf becomes negative, the output of the limiter circuit 52 becomes negative, and therefore the upper limit value of the control voltage limiter circuit 11 (still 111) decreases. When the upper limit value of the control voltage limiter circuit 11 (or 11') decreases, the control voltage at the DC voltage determining terminal decreases, reducing the DC voltage, and as a result, the DC voltage Pd decreases. Effects similar to those of the embodiment can be obtained.

Furthermore, it goes without saying that the control circuit 51 can also be realized by a computer program or the like having the same functions.

Furthermore, although thyristors were used in the above embodiments, it is also possible to apply a structure using a thyristor or the like.

In addition, the present invention can be modified and implemented in various ways without changing the gist thereof.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, in an AC/DC converter directly connected to a generator, when the frequency of the generator drops below a predetermined value at startup, the AC/DC converter converts the AC/DC converter according to the frequency fluctuation. Since the AC/DC converter is operated with a reduced DC voltage, it is possible to provide a highly reliable starting method for the AC/DC converter that can perform extremely stable starting operation.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an AC/DC converter, Fig. 2 is a diagram showing the 9 turns of startup of a conventional converter, Fig. 3 is a diagram showing a load start-up pattern of the output of a nuclear power generator, and Fig. 4 5 is a block diagram showing one embodiment of the invention, FIG. 5 is a diagram for explaining the invention in detail, and FIG. 6 is a block diagram showing another embodiment of the invention. 1.1'... AC bus, 2, 2'... Conversion transformer, 3.3'... Converter, 4, 4'... Smoothing reactor, 5... DC transmission line, 6, 6'...P-T, 7
．． 7'...C・T, 8.8'...constant current control circuit,
9,9'...constant voltage, 10.10'...control voltage selection circuit, 11゜11'...control voltage limiter circuit,
12, 12'... Ignition phase control circuit, 51... Control circuit, 52... Limiter circuit. Applicant's agent Patent attorney Takehiko Suzue 13-

Claims (1)

[Claims] In an AC/DC switching device directly connected to a generator that converts alternating current to direct current or direct current to alternating current by controlling a υ converter by a control device, when the frequency of the generator falls below a predetermined value at the time of startup. A method for starting an AC/DC converter, characterized in that the AC/DC converter is operated by reducing the DC voltage of the AC/DC converter in response to fluctuations in the frequency.